small room acoustics, speaker directivity and dynamics

[oivavoi]

I do!
https://www.cnet.com/uk/products/sony-str-da1200es/review/

I like it! But how sensitive are your drivers, @Cosmik ? I just saw this model selling for virtually nothing here in Norway, and I'm considering to use it for my coming setup with the morrison speakers. It's virtually impossible to find a multichannel amp with a volume control that controls all the channels at the same time... so an AVR like this might be the best choice, whcn simplicity is the goal.

The only thing I'm concerned about is dynamics, whether there's enough power there. I want to be able to reach transient peaks of 110 db, and I'm not sure that 100 watts for the woofer will cut it... (89 db sensitivity). On the other hand, it would give me great pleasure to achieve great sound with speakers I expect to be astonishing with a super cheap amp.

 

[Cosmik]

But how sensitive are your drivers

I really don't know... The amp's instruction manual says that it will protect itself, so I think you can do the experiment pretty safely. It can, apparently, do 100W no problem, and 130W at higher distortion, so I think you are just about OK for your wall-shaking volume requirement!

 

[RayDunzl]

I want to be able to reach transient peaks of 110 db, and I'm not sure that 100 watts for the woofer will cut it...

Hmm...

Repeating 50hz Risset Drum on the four 150W (rated) cheezewoofers (57Hz low crossover). They don't seem to be in distress... Lots of rattles around the room.

 

[Cosmik]

Repeating 50hz Risset Drum on the four 150W (rated) cheezewoofers (57Hz low crossover).

Looks to have a very distinctive positive (asymmetrical) peak at the start. In the case of the dipole speaker (if I understand the way people are using them), a negative version of that peak flies out of the back, waiting to be reflected towards the listener.

The "law of the first wavefront" was described and named in 1948 by Lothar Cremer.
The "precedence effect" was described and named in 1949 by Wallach et al. They showed that when two identical sounds are presented in close succession...

https://en.wikipedia.org/wiki/Precedence_effect

So with the dipole, the first "wavefront" is positive, followed by a delayed negative version; the two sounds are most definitely not "identical"...

 

[oivavoi]

I really don't know... The amp's instruction manual says that it will protect itself, so I think you can do the experiment pretty safely. It can, apparently, do 100W no problem, and 130W at higher distortion, so I think you are just about OK for your wall-shaking volume requirement!

Thanks! Dynamics is one of the areas which I think are least understood when it comes to sound reproduction, both theoretically/rationally/measurement-wise, and when it comes to perception and psychoacoustics. I'm not aware of any studies on it, at least.

My hunch, however, is that most systems are underpowered, and are unable to do full justice to the dynamic transients in music, which may have short bursts that are much louder than the average. One may still be able to play loud - an average of 90 db is louder than I ever go - but it might be that this leads to soft clipping of transients, and makes the music sound "softer" than it would otherwise do in a system that can reproduce all of the peaks in recordings where they have been preserved.

 

[svart-hvitt]

Thanks! Dynamics is one of the areas which I think are least understood when it comes to sound reproduction, both theoretically/rationally/measurement-wise, and when it comes to perception and psychoacoustics. I'm not aware of any studies on it, at least.

My hunch, however, is that most systems are underpowered, and are unable to do full justice to the dynamic transients in music, which may have short bursts that are much louder than the average. One may still be able to play loud - an average of 90 db is louder than I ever go - but it might be that this leads to soft clipping of transients, and makes the music sound "softer" than it would otherwise do in a system that can reproduce all of the peaks in recordings where they have been preserved.

Peak transients are very seldom higher than 30 dB over main material.

Please correct me (or link me to a song on Tidal etc.) if I'm wrong.

So it seems like say 35 dB headroom is all you'd ever need.

Which means 120 dB capacity is all you need. Isn't it?

 

[Cosmik]

Thanks! Dynamics is one of the areas which I think are least understood when it comes to sound reproduction, both theoretically/rationally/measurement-wise, and when it comes to perception and psychoacoustics. I'm not aware of any studies on it, at least.

My hunch, however, is that most systems are underpowered, and are unable to do full justice to the dynamic transients in music, which may have short bursts that are much louder than the average. One may still be able to play loud - an average of 90 db is louder than I ever go - but it might be that this leads to soft clipping of transients, and makes the music sound "softer" than it would otherwise do in a system that can reproduce all of the peaks in recordings where they have been preserved.

I would like to think that an amp that can reproduce a 20 kHz sine wave at full power into the stiffest load can do the dynamics, but it isn't proven by the normal tests - as @Ken Newton was saying, I think.

 

[oivavoi]

You might be right, Svarthvitt!

Just to explain what I mean: The choir I'm singing in recently performed a piece by the Scottish composer James Macmillan, St Luke's Passion. One of the guys in the choir is an amateur producer, and recorded it. Here's the recording in its original form, without any post-editing: https://www.dropbox.com/s/bldc4f0x1okmaky/st luke passion konsert original klippet.wav?dl=0

When I listen to this recording over my system, I just KNOW that a lot of the original dynamics from our performance is gone. It just ain't there. My perception from standing in the choir and close to the orchestra will of course be different from how it's perceived in the audience. But still. I would be willing to bet 10 cables from Nordost that this recording is less dynamic than how it was there and then when we performed the piece. When I listen to this, I have a strong feeling that something has been lost, and that the original acoustic event isn't being realistically rendered. It's not about tonality or imaging, it's about force, silence and dynamics.

Why is that? One limitation might be with the recording equipment (which, if I remember correctly, was decent but not super expensive, so probably with a somewhat limited dynamic range). But it can also have to do with my own system, which might not be able to do justice to the dynamics that might be in the recording.

 

[Frank Dernie]

You might be right, Svarthvitt!

Just to explain what I mean: The choir I'm singing in recently performed a piece by the Scottish composer James Macmillan, St Luke's Passion. One of the guys in the choir is an amateur producer, and recorded it. Here's the recording in its original form, without any post-editing: https://www.dropbox.com/s/bldc4f0x1okmaky/st luke passion konsert original klippet.wav?dl=0

When I listen to this recording over my system, I just KNOW that a lot of the original dynamics from our performance is gone. It just ain't there. My perception from standing in the choir and close to the orchestra will of course be different from how it's perceived in the audience. But still. I would be willing to bet 10 cables from Nordost that this recording is less dynamic than how it was there and then when we performed the piece. When I listen to this, I have a strong feeling that something has been lost, and that the original acoustic event isn't being realistically rendered. It's not about tonality or imaging, it's about force, silence and dynamics.

Why is that? One limitation might be with the recording equipment (which, if I remember correctly, was decent but not super expensive, so probably with a somewhat limited dynamic range). But it can also have to do with my own system, which might not be able to do justice to the dynamics that might be in the recording.

IME the microphone choice and particularly their placement makes the most difference to the recorded sound. Our ears hear through a lot of acoustic deviations, microphones do not.
I used to try to set up my microphones (never tried more than 2) during rehearsal and keep listening to bits of sample recording until I got a good balance.
About 1m over the conductors head was a good starting point, or if that was impossible I used PZM microphones on the floor, but not nearly as good.

 

[Cosmik]

You might be right, Svarthvitt!

Just to explain what I mean: The choir I'm singing in recently performed a piece by the Scottish composer James Macmillan, St Luke's Passion. One of the guys in the choir is an amateur producer, and recorded it. Here's the recording in its original form, without any post-editing: https://www.dropbox.com/s/bldc4f0x1okmaky/st luke passion konsert original klippet.wa
When I listen to this recording over my system, I just KNOW that a lot of the original dynamics from our performance is gone. It just ain't there. My perception from standing in the choir and close to the orchestra will of course be different from how it's perceived in the audience. But still. I would be willing to bet 10 cables from Nordost that this recording is less dynamic than how it was there and then when we performed the piece. When I listen to this, I have a strong feeling that something has been lost, and that the original acoustic event isn't being realistically rendered. It's not about tonality or imaging, it's about force, silence and dynamics.

Why is that? One limitation might be with the recording equipment (which, if I remember correctly, was decent but not super expensive, so probably with a somewhat limited dynamic range). But it can also have to do with my own system, which might not be able to do justice to the dynamics that might be in the recording.

Listening to it now. So did the producer use any dynamic compression or limiting? It would be very interesting to know.

I am guessing that reverberation and ambience will always 'smooth out' the dynamics, and maybe we are hearing a different balance than you get in the choir.

My expectation is that it's quite hard to 'lose' dynamics without a clever variable gain doodah somewhere in the chain - or appreciable clipping/distortion which, presumably, we have not got here.

(You all sound very good, btw!)

More on how the direct/ambient balance affects the dynamics:
http://www.regonaudio.com/Why Recorded Music Sounds Too Aggressive.html

There is a second effect that is more subtle, but is perhaps even more important musically: The hall eats transients. Distance attenuates the direct sound, the first arrival of the initial transient. But the reverberation picks up and amplifies the steady, tonal part of the sound. The transient part is not amplified in the same way because it is over long before the 100 milliseconds (=1/10 sec) rise time of the reverberation.

You can think of this in another way: The hall acts on sounds as a kind of time-delayed amplifier. The reverberation, all those later reflections combined, amplify the sounds made on stage. But the process spreads out transients. They contribute their energy to the reverberant field, all right. But that energy is spread in time and therefore is not as "transient" as the transient sound directly from the instruments.

So what happens? The sound in the hall is much less transient-laden, far smoother, far more legato, far less staccato, less "bangy" and "crunchy," than close-up sound. It is also harder to understand the words at a distance. Theaters for speech (plays, etc.) have to have much less reverberation than a concert hall in order for speech to be comprehensible (speech comprehensibility depends on transient definition).

You are hearing the 'close mic'ed' version he talks about when you are in the choir, but the audience (and this non close-mic'ed recording) is hearing the 'smoothed out' version.

 

[oivavoi]

Listening to it now. So did the producer use any dynamic compression or limiting? It would be very interesting to know.

I am guessing that reverberation and ambience will always 'smooth out' the dynamics, and maybe we are hearing a different balance than you get in the choir.

More on how the direct/ambient balance affects the dynamics:
http://www.regonaudio.com/Why Recorded Music Sounds Too Aggressive.html

You are hearing the 'close mic'ed' version he talks about when you are in the choir, but the audience (and this non close-mic'ed recording) is hearing the 'smoothed out' version.

Thanks, these are excellent points! The explanation about "close mic'ed" sound that I'm hearing standing in the choir, vs the smoothed out sound that the mics pick up farther down in the venue, seems like the explanation that would make old Ockham most happy. Easy and rational explanation.
(afaik the recording guy in the choir didn't use any limiters etc)

Btw, this is also in line with reasoning I read from Martijn Mensink from Dutch & Dutch on Diyaudio some time back. Seriously, this young designer seems to be one of the most rational guys making audio products these days.

I once had a regular 7" 2-way. In my opinion it struggled at higher volume levels, making the sound less dynamic and shrill. However, when I listened to these speakers outside in the open, this appeared not to be the case. I could push them really hard, to just below audible distortion without really noticeable compression or otherwise lack of dynamics.

My hypothesis has since been that dynamics are to a great extent related to the level of reflected sound. In a room with lively acoustics a low directivity speaker that is perfectly coping with the signal it is offered, may not sound very dynamic, while a small speaker with higher directivity that is pushed quite hard in a more damped room may sound more dynamic. It is not so much the short loud sound that gives the sense of dynamics, but the silence before the storm - the short quiet between for instance the hits of a snare drum. In the situation with more reverb and reflections the quiet part is just never as quiet as it could be.
(...)
Imagine a situation in a gymnasium: a listener is situated relatively far from hypothetically perfect (no compression/distortion at all), but low DI speakers. The room has little acoustic damping (high RT) and the room is strongly illuminated. Although the speakers don't compress, it probably will not sound very dynamic. Sound levels don't rise and die away quickly.

Following that same rationale, a speaker with high directivity will probably sound more dynamic under those same conditions, but anything you could do to increase the direct/reverberant ratio (sit closer, increase acoustic damping) would probably increase subjective dynamics. At some point you may however overdo it, because aspects such as spaciousness suffer too much.

So if this is correct, it may be that my obsession with high-powered amps is unnecessary, and the best way to increase dynamics simply is to sit closer to the speakers.

 

[oivavoi]

«Sit closer»...

I liked that one.

Nearfields for everyone!?

Perhaps I like near-field listening, at least! I find it more involving.

But I'm still not entirely convinced that it's a bad idea with a lot of amplifier power. One may think about this scenario: Imagine that our concert was close-mic'ed and the full attack of the transients had been preserved in the recording - how much power would it take to really reproduce that?

And the same Mensink still landed on these principles when designing the 8C's, despite his ideas that dynamics to a large degree is about room acoustics:
"Dynamic range, high power handling, oversized amps for non-compressed transients and high S/R ratio".

Dutch & Dutch may be wrong on this, of course, but I'm not entirely sure they are wrong. At the moment this is my one concession to audiophilia nevrosa.

 

[Jakob1863]

@oivavoi

<snip>
But I'm still not entirely convinced that it's a bad idea with a lot of amplifier power. One may think about this scenario: Imagine that our concert was close-mic'ed and the full attack of the transients had been preserved in the recording - how much power would it take to really reproduce that?

It depends on to many parameters (dynamic range of your performance, volume of the room, distance to the speakers and of course the efficiency of the speakers).
Even in a small room with "normal" volume (very loud but not uncomfortable) running into clipping of power amplifiers at ~350W was easy when using large electrostats with efficiency even lower than the already low speced number (should have 86dB/1W/8Ohms, but it was more around 80dB).
Edit: forgot to mention, music was modern orchestral music with quite impressive dynamic range

And the same Mensink still landed on these principles when designing the 8C's, despite his ideas that dynamics to a large degree is about room acoustics:
"Dynamic range, high power handling, oversized amps for non-compressed transients and high S/R ratio".

Dutch & Dutch may be wrong on this, of course, but I'm not entirely sure they are wrong. At the moment this is my one concession to audiophilia nevrosa.

Maybe we should start another thread on small room acoustics and the relationsship between room acoustics and different speaker directivity and listener perception.

 

[SIY]

I ran a dynamic range analysis on the St Luke Passion recording (attached). That result is superb. Most commercial recordings are well under 10 (usually 6-8), my home recordings go to about 15. Well done, sir.

 

[oivavoi]

I ran a dynamic range analysis on the St Luke Passion recording (attached). That result is superb. Most commercial recordings are well under 10 (usually 6-8), my home recordings go to about 15. Well done, sir.

Cool! I had no idea. I will tell it to the guy who made the recording, I'm sure he will be happy to hear it.

It depends on to many parameters (dynamic range of your performance, volume of the room, distance to the speakers and of course the efficiency of the speakers).
Even in a small room with "normal" volume (very loud but not uncomfortable) running into clipping of power amplifiers at ~350W was easy when using large electrostats with efficiency even lower than the already low speced number (should have 86dB/1W/8Ohms, but it was more around 80dB).
Edit: forgot to mention, music was modern orchestral music with quite impressive dynamic range

Maybe we should start another thread on small room acoustics and the relationsship between room acoustics and different speaker directivity and listener perception.

Looks like Thomas created the new thread for us

What I'm wondering: What would be the way to measure things like amplifier power, clipping and dynamics - how much one "needs"? I asked B&O's Geoff Martin about it over at his blog, and he said that it's easy for them because they do active speakers. They start with a given goal for SPL, and look at how much driver movement/cone area they need to achieve that. Then they simply look at the xmax of their drivers, calculate how much power is needed to drive the drivers to the max, and install amps which have enough power to do that.

Looking at the problem this way avoids the problem of subjectivity and perceived dynamics - it simply tries to find the optimum performance given the drivers at hand.

But room acoustics is probably also vital here, maybe more so than amp power etc. It's telling that even here at this forum we get so hung up on boxes and specifications and perception of boxes, instead of talking about room acoustics and speaker performance, which it's more difficult to change and influence... audiophiles will be audiophiles.

 

[RayDunzl]

Looks to have a very distinctive positive (asymmetrical) peak at the start. In the case of the dipole speaker (if I understand the way people are using them), a negative version of that peak flies out of the back, waiting to be reflected towards the listener.

Your anti-dipole bias is showing.

Only the cheezewoofers were active - Dayton Sub-1500 - cone in the front of a bottom ported box.

The waveform shown was the source wave, not the in-air.

 

[oivavoi]

Anti-dipole folk be like

 

[Frank Dernie]

http://www.sanderssoundsystems.com/technical-white-papers/52-esl-amp-white-paper
http://www.sanderssoundsystems.com/technical-white-papers/172-tubes-vs-transistors

 

[oivavoi]

http://www.sanderssoundsystems.com/technical-white-papers/172-tubes-vs-transistors

Thanks. This quote from the article is indeed fascinating:

To see what is going on with an amp when playing music only requires an oscilloscope. These are very fast (the slowest ones will show 20 MHz) and will clearly show amplifier peak clipping when music is playing. A meter is too slow to do so. A 'scope is cheap (you can get them for $100 on eBay all day long). So you don't have to take my word for what I am about to explain. Feel free to get your own 'scope and examine your system's performance.

You simply connect the 'scope across your speaker or amplifier terminals (which are electrically the same), adjust the horizontal sweep as slow as you can while still seeing a horizontal line on the screen. Don't go so slowly that you see a moving dot.

Now play dynamic music at the normally loud levels you enjoy. Adjust the vertical gain on the 'scope so that the trace stays on the screen.

As music plays, you will clearly see if clipping occurs. The trace (which will just be a jumble of squiggly lines) will appear to hit an invisible brick wall. It will appear as though somebody took a pair of scissors and clipped off the top of the trace. That's where the term "clipping" comes from.

If you see clipping at the levels you like to listen, then you are not using a sufficiently powerful amplifier to play your music cleanly. Your system is compromised because your amplifier will have compressed dynamics, sound strained, lose its detail, and have high levels of distortion.

The 'scope will be calibrated so that you will know the voltage at which clipping occurs by observing the grid lines. If you know the voltage and the impedance of your speakers, you can easily calculate the power.

Power is the voltage squared, divided by the impedance. So if the 'scope measures 40 volts at clipping, and you are driving 8 ohm speakers, you know that 200 watts are being produced at clipping -- and this is insufficient power for your particular system because it is clipping.

You will find that conventional, direct-radiator (not horn-loaded), magnetic speaker systems of around 90 dB sensitivity, require around 500 watts/channel to avoid clipping. More power is needed in larger rooms or if you like to play your music more loudly than most.

 

[svart-hvitt]

You might be right, Svarthvitt!

Just to explain what I mean: The choir I'm singing in recently performed a piece by the Scottish composer James Macmillan, St Luke's Passion. One of the guys in the choir is an amateur producer, and recorded it. Here's the recording in its original form, without any post-editing: https://www.dropbox.com/s/bldc4f0x1okmaky/st luke passion konsert original klippet.wav?dl=0

When I listen to this recording over my system, I just KNOW that a lot of the original dynamics from our performance is gone. It just ain't there. My perception from standing in the choir and close to the orchestra will of course be different from how it's perceived in the audience. But still. I would be willing to bet 10 cables from Nordost that this recording is less dynamic than how it was there and then when we performed the piece. When I listen to this, I have a strong feeling that something has been lost, and that the original acoustic event isn't being realistically rendered. It's not about tonality or imaging, it's about force, silence and dynamics.

Why is that? One limitation might be with the recording equipment (which, if I remember correctly, was decent but not super expensive, so probably with a somewhat limited dynamic range). But it can also have to do with my own system, which might not be able to do justice to the dynamics that might be in the recording.

@oivavoi , how does this recording sound on the parameters you mentioned above on your DD8c speakers, which you have purchased in the meantime?